Soils: Krum Complex and Tarrant Association (Gently Undulating)

Known: Area in inner cantonment where small arms ammunition and metal ammunition parts were disposed in two trenches. Some scrap metal appears to have melted and cooled, indicating that waste material may have been burned in the trenches.

Previous Investigations: Previous investigations at the site include a geophysical survey, a soil gas survey, and drilling and sampling of soil borings. The geophysical survey indicated that there are two northwest-southeast trending trenches (shown in Figure B28-1) containing buried metal. The northern trench is approximately 300 feet long and 15 feet wide. The southern trench is approximately 100 feet long and 15 feet wide. The trenches were shallow (less than 5 feet deep) as evidenced by field observations where the northern trench intersects the drainage ditch. Because the trenches were so shallow, and were in soil, the trenches caved in and the ground surface was leveled off during UXO removal activities.

A soil gas survey was conducted at the site in 1995. In soil gas, PCE was detected at a maximum concentration of 0.70 ug/L. Six surface soil samples were collected at the site in 1995. Low levels of phthalates were detected in two of the surface soil samples. None of the metals levels exceeded background (RRS1) levels.

A total of six soil borings were drilled and sampled at the site. Analytical chemistry data generated during this investigation was performed by Chemron, Inc. and has been validated. No VOCs were detected in the samples. Phthalates were detected in three samples. Chromium was detected in limestone in three borings at concentrations exceeding background (RRS1) levels. One groundwater grab sample was collected from B28-SB3; results are provided in Table B28-2.

In March 1997, UXO identification work was initiated at the site. As part of this effort, the trenches were excavated so that the material could be sifted to remove scrap metal and UXO. These sifting operations commenced in June 1997 and were completed in September 1997. A total of approximately 600 cubic yards of soil and waste materials were removed and sifted, and one sample of sifted soil was collected and analyzed by ITS Laboratory for VOCs, explosives, and metals.

Resampling Activities: Parsons ES proposes that no rework be conducted at SWMU B-28. Only one sample of sifted soil was analyzed by ITS Laboratory. Since a soil pile disposition assessment is currently planned for SWMU B-28 under RL83, it is proposed that the ITS results be used for screening purposes.